ETYM Old Eng. ordre, French ordre, from Latin ordo, ordinis. Related to Ordain, Ordinal.
In biological classification, a group of related families. For example, the horse, rhinoceros, and tapir families are grouped in the order Perissodactyla, the odd-toed ungulates, because they all have either one or three toes on each foot. The names of orders are not shown in italic (unlike genus and species names) and by convention they have the ending “-formes” in birds and fish; “-a” in mammals, amphibians, reptiles, and other animals; and “-ales” in fungi and plants. Related orders are grouped together in a class.
1. Putting in order; SYN. ordering.
2. A degree in a continuum of size or quantity; SYN. order of magnitude.
3. Established customary state esp. of society.
4. A commercial document used to request someone to supply something in return for payment; SYN. purchase order.
5. A body of rules followed by an assembly; SYN. rules of order, parliamentary law, parliamentary procedure.
6. (Often plural) A command given by a superior (e.g., a military or law enforcement officer) that must be obeyed.
7. (Biology) Taxonomic group containing one or more families.